Turd in the Swimming Pool

It was supposed to be a small birthday dinner for my mom but then assorted second-string relatives got wind of it and started inviting themselves.  Before I knew it our small family meal turned into dinner for 18, including Sharon.
Sharon is an unwelcome growth on our family tree. The future ex-wife (we hope) of my second cousin, she is one of those boisterous women whose brain is apparently without any type of filter, so that whatever she thinks is exactly what she says.
As in any large family, we all know where the skeletons are buried,  but our shaky family harmony is based on a combination of avoidance and denial: there are topics that are simply Not Discussed. Whether Sharon is malicious or simply an idiot is a source of frequent debate, but our tenuous hold on peace is threatened whenever she opens  her mouth.
The party was progressing pleasantly, but  then Sharon, her husband and their infant son unexpectedly arrived, and the room got very silent. “Sharon is here,” my first cousin informed me without enthusiasm, even though Sharon is her daughter-in-law.  She sighed.  “Seeing  that girl is like finding a turd in the swimming pool,” she said.
Sharon swept grandly into the room as though expecting applause; she stopped, turned around and  sniffed. “What on earth are you cooking?”  she asked me, “Fried carp?” and she declared her need for a drink.
I hate when Sharon drinks, because she tends to fall down the stairs or walk into sliding glass doors. (One memorable Thanksgiving she did both.)  This day, she walked in with the baby under one arm and a bottle of vodka under the other.  Although family protocol does not permit us to discuss  anything too personal, I approached my favorite niece. “Does Sharon have a drinking problem?”  I  asked.
“Well,”  she said, “she did graduate from the University of Florida,” as if that explained everything.  Later, we were treated to the jaw dropping  spectacle of Sharon breastfeeding the baby while sipping a martini.
After the baby was fed, Sharon decided to socialize. First, she  approached  my  nephew whose house is in foreclosure. “Are you living on the street yet?”  she asked.
Next,  Sharon chatted up my older  brother who just turned 60. “I’ll bet you were really good looking when you were young,” she remarked, before turning to my middle sister, who  has no children. “I love your house,”  said Sharon,  “would you leave it to me when you die?”
Moving on, a trail of dropped jaws in her wake,   she asked my step-nephew if his porn addiction put a strain on his marriage, and then she asked my sister-in-law when her son would be eligible for parole.
When we finally sat down to dinner there was a noticeable chill in the air. Faces were frozen with brittle little smiles and wineglasses were clutched so hard they threatened to snap. Her mouth full, Sharon asked my younger brother about his faulty prostate and  asked my nephew if his wife was still cheating on him.
Chalking this up as yet another disastrous dinner party,  it was finally time for dessert. We serenaded  my mom with a warbling version of “Happy Birthday” ending with “….and many mooooore!”  In the second before Mom blew the candles  we heard Sharon say, “She’s 89; how many more can she have?”
My sister-in-law shifted dangerously in her chair. “Tell me, Sharon,” she began ominously, “are you drunk or are you an idiot? We’ve all been wondering.”  And in the absolute silence that followed the illusion of family harmony shattered like glass.